Coreactive Polymer Alloys - American Chemical Society

Chapter 3

Coreactive Polymer Alloys 1

M. Lambla, R. X. Yu , and S. Lorek

Downloaded by MONASH UNIV on November 29, 2015 | http://pubs.acs.org Publication Date: July 21, 1989 | doi: 10.1021/bk-1989-0395.ch003

Ecole d'Application des Hauts Polymères, Institut Charles Sadron (CRM-EAHP), F-67000 Strasbourg, France

The sales of plastics continue to increase in a large part due to technical and economic advancements of polymer blends. Reactive blending is a useful technique for elastomers but, i t appears that chemistry could also play an important role in the correct microstructure adjustment of thermoplastic alloys. Interfacial reactivity should be the focal point in maintaining the expected structure during subsequent stages of manufacture. Besides industrial examples, various kinds of polymeric co-reacting systems are also presented in order to emphasise the key factors of reactive blending. H i s t o r i c a l l y , reactive blending has been associated with the manufacture of elastomeric-based products. In the future, although elastomers or thermosets w i l l continue to play an important role, reactive blending w i l l expand to the production of thermoplastic a l l o y s . The reactive processing may provide viable mechanisms for the creation and preservation of the desired blends with controlled structure and morphology, and assures that the microstructure i s maintained throughout the subsequent stages of manufacturing. This paper w i l l deal with a general overview of s i g n i f i c a n t i n d u s t r i a l developments i n this f i e l d , whereas the key factors i n reactive blending w i l l be i l l u s t r a t e d mainly with results from laboratory studies. GENERAL CHARACTERISTICS OF BLENDS Most polymer mixtures phase separate, as the entropy of mixing of the polymeric species i s very low and the enthalpy of mixing i s p o s i t i v e . Blends with a multiphase quenched structure are obtained by suitable melt-blending at high temperature and subsequent cooling below glass or c r y s t a l l i s a t i o n temperature. These blends may display a wide range of improved properties i n comparison to pure homo or copolymers. The most important factors governing the mechanical properties of incompatible polymer blends are: the interfacial adhesion between separated 1

Current address: University of Nanjing, China 0097-6156/89/0395-0067$06.00A) o 1989 American Chemical Society

In Multiphase Polymers: Blends and Ionomers; Utracki, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

68

MULTIPHASE POLYMERS: BLENDS AND IONOMERS


phases and the morphology, i . e . the size and shape of the dispersed phase. The greatest toughness i s achieved when the i n t e r p a r t i c l e distance i s smaller then a c r i t i c a l value (1), depending on the way the fracture energy i s dissipated. Morphology of the dispersed phase depends on complex shear and elongational deformations to which the materials are subjected during melt-blending. However, the size and shape of the dispersed phase are also controlled by i n t e r f a c i a l tension (2) and viscoelastic properties of the components. Hence, by adding an appropriate emulsifying agent, the i n t e r f a c i a l tension and p a r t i c l e size may be varied over a wide range. The use of block or graft copolymers i s quite a common and versatile method for reducing p a r t i c l e size and enhancing i n t e r f a c i a l adhesion i n incompatible blends. A schematic representation of this feature i s given i n Figure 1 ; the emulsifying e f f e c t s of block and graft copolymers have been previously demonstrated i n several systems (3). A theoretical approach of t h i s behaviour has been discussed recently by LEIBLER (4). The block or grafted copolymers are generally prepared separately and introduced i n low concentrations (1 - 3 wt %) i n the meltmixing system, which i s based on two incompatible resins. It i s also possible to create these amphiphilic agents i n s i t u by chemical r e a c t i v i t y based on end-capping or grafting reactions. EISENBERG (5) has also shown that ionic interactions can be used to control the degree of m i s c i b i l i t y of otherwise immiscible polymer systems. In some of these, the interactions are based on proton transfer from a donor s i t e on one polymer to an acceptor s i t e on another polymer, leading to ion-ion interactions. In others, the transfer of a metal cation from an ionomer to a polar polymer i s the r e s u l t of an ion-dipole interaction. More recently, JEROME and TEYSSIE (6) have confirmed the advantage of ionic-cross interactions between sulphon (or carboxyl)) and t e r t i a r y amine chain end-groups. The phase separation i s controlled by the content and strength of the ion-pairs, as shown by SAXS characterization. Thus, i t appears that chemical r e a c t i v i t y or ionic-cross i n t e r actions could lead to i n s i t u compatibilising or m i s c i b i l i t y enhancement during melt-mixing. However, several questions remain. How does the r e a c t i v i t y modify the thermodynamic balance, the reciprocal m i s c i b i l i t y or the rheological behaviour of the melt? Or, how the covalent or ionic bonding influence the i n t e r f a c i a l adhesion processability and f i n a l mechanical properties of the immiscible blends ? EXAMPLES FROM INDUSTRY Among the numerous examples from industry, one of the f i r s t successf u l ones was based on reactive blending of polyamide and ethylenepropylene modified rubbers, containing grafted carboxylated


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Coreactive Polymer Alloys

LAMBLAETAL.

69


or anhydride groups. In this case, approximately 1 wt% of carboxyl or anhydride groups was s u f f i c i e n t to create a graft product by condensation reaction with the amino-terminated polyamide, as described by CIMMINO and coworkers (7) and others (8-10). The important parameters are rubber concentration and p a r t i c l e s i z e . An increasing rubber content and a decreasing p a r t i c l e diameter s h i f t the brittle-tough t r a n s i t i o n to lower temperature, while the impact strength at very low temperature increases, as shown by BORGGREVE (11). A similar idea of functional grafting was also applied by DOW Chemicals i n a system based on styrenic copolymers containing oxazoline groups (RPS). These resins were mixed with carboxylated polyolefins. The reaction scheme i s indicated i n Figure 2, and Table 1 summarises the mechanical properties of pure homopolymers as compared to those obtained from a mixture of 50% by weight of the two reactive copolymers (12). I t i s interesting to note that most f i n a l properties of the reactive blends show the expected intermediate values. These kinds of reactive copolymers produced by c l a s s i c a l synthesis or by grafting could i n c i t e future d i v e r s i f i c a t i o n i n reactive mixing, even with o l e f i n i c products, as mentioned by G0T0H et a l . , (13). Due to the excellent price/performance ratio, polypropylene should not only be a good base f o r unreactive blends, widely used i n automotive industry, but also an a t t r a c t i v e product for reactive blending. However, i t i s necessary to introduce polar reactive groups i n the main chain which i s d i f f i c u l t

Table 1. Reactive Polystyrene Blends

RPS

LDPE

50/50 BLEND

TENSILE YIELD (MPa)

36.5

6.9

20

TENSILE MODULUS (MPa)

2890

ELONGATION (%)

2

NOTCHED IZOD IMPACT (FT-LB/ (INCH))

0.2

VICAT (°C)

42

MELT FLOW (g/10 mn)

7

SPECIFIC GRAVITY

1.04

124

690

600

75

NB

13

28

31

5

4

0.94

0.98




F i g u r e 2: R e a c t i o n scheme o f r e a c t i v e p o l y s t y r e n e blends .


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LAMBLA ET AL.



or impossible i n synthesis by ZIEGLER NATTA c a t a l y s i s or by grafting. Monomer grafting onto propylene by r a d i c a l reactions is generally accompanied by chain degradation and related decrease in mechanical strength but, as i t w i l l be shown, considerable progress has been made recently i n this f i e l d . Polybutylene therephthalate (PBT) has been used as a blend component to provide chemical resistance i n various systems, but the most interesting one results from a combination with polycarbonate and, eventually, an impact modifier of the cores h e l l type. Polyester blends containing polycarbonate exhibit ester interchange chemical reactions, which add to the complexity of property control of these materials. DEVAUX and co-workers (14) have examined the t r a n s e s t e r i f i c a t i o n reaction catalysed by residual catalysts i n PBT which can lead to the formation of block and random copolymers. They have shown that a l l y l or aryl phosphites inactivate the residual titanium catalyst and minimise the t r a n s e s t e r i f i c a t i o n reaction. HOBBS et a l . (15) reported a way of c o n t r o l l i n g m i s c i b i l i t y behaviour, morphology and deformation mechanisms, i n order to obtain blends compatib i l i s a t i o n and excellent mechanical properties. There are two further p o s s i b i l i t i e s for preventing segregation in complex immiscible mixtures. The f i r s t one implies crossl i n k i n g reaction of the dispersed phase, associated with i n t e r f a c i a l bonding and leads to the well-known dynamic vulcanisation (17). The second one results from mechanical interlocking of the phases which are created i n interpenetrated polymer networks (IPN). It i s worthwhile to note that chemistry plays a major role in the morphology and control of mechanical properties i n complex systems l i k e PPE blends with c r y s t a l l i n e polymers, such as polyolefins, polyamides (PA) and polyesters (18). The amount of copolymer formed during the reactive extrusion between functionalised PPE and PA has a s i g n i f i c a n t effect on the impact-strength of blends. The l a t t e r levels o f f only above 10% of copolymer. Clearly, chemistry has been most helpful i n the development of i n d u s t r i a l blends. Nevertheless, i n many cases, the basic reaction conditions are not completely understood. The following i s a description of laboratory studies carried out to examine the i n t e r f a c i a l r e a c t i v i t y and two kinds of condensation reactions in immiscible polymer blends. LABORATORY EXPERIMENTS AND

FURTHER STUDIES

As mentioned above, d i r e c t compatibilisation by melt blending could be obtained by functional end-capping or grafting reactions, or again by interpolymeric bonding through a reagent which i s able to react with both polymeric species. This l a s t system w i l l be examined f i r s t of a l l , i n the case of a mixture based on a polystyrene matrix containing dispersed polyolefinic


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72


nodules, where the reactive product i s bis-maleimide (BM). The f i r s t functional g r a f t i n g studies were performed i n a system containing a copolymer of methylmethacrylate and maleic anhydride as well as styrenic hydroxylated oligomers, both amorphous products. The second system was based on two semi-crystalline polymers : polypropylene and polyamide. To attain potential reactivity, polypropylene was f i r s t grafted with maleic anhydride and the results of this radicalar melt-grafting are presented. The f i n a l blend was obtained i n one-step extruding of the two homopolymers and the reactive polypropylene.


INTERFACIAL REACTIVE BLENDING Polystyrene (PS) and low density polyethylene (LDPE) are two incompatible polymers and t h e i r blends obtained by melt-mixing show very poor mechanical properties i n comparison to the high impact polystyrenes obtained by direct synthesis i n the presence of polybutadiene. In order to obtain a better quality of dispersion, i . e . regular and smaller p a r t i c l e size d i s t r i b u t i o n , i t i s possible to add hydrogenated block copolymers of styrene and butadiene (SBS). Some of these products are supplied commercially by SHELL, under the tradename : KRATON G. While investigating the same model system, TEYSSIE et a l . , (19) have synthesised a large range of pure or "tapered" poly(styrene-b-hydrogenated polybutadiene)diblocks. Their main results can be summarised as follows : - the dispersed phase mean size decreases to the sub-micron l e v e l , depending on concentration and structural c h a r a c t e r i s t i c s (20) ; - the bulk physico-mechanical properties of these blends are s t r i k i n g l y improved by the presence of the copolymer (21). However, the p o l y o l e f i n i c dispersed phase cannot contribute to a large increase i n impact performance, due to i t s c r y s t a l l i n e structure, as shown previously by HEIKENS et a l . (22). In order to v e r i f y this point, a low concentration of atactic polypropylene was introduced i n certain blends i n the p o l y o l e f i n phase. Studies of the i n t e r f a c i a l and/or bulk r e a c t i v i t y were performed by adding BM, which i s a difunctional highly reactive molecule. The two double-bonds are sensitive to r a d i c a l attack and quite e f f i c i e n t i n addition reactions on t e r t i a r y hydrocarbon s i t e s . In a previous study we established that c l a s s i c a l peroxydes could not play the major role i n i n t e r f a c i a l bonding. Bulk reactions, especially i n polystyrene matrix, lead to chain degradation and related decrease of mechanical strength. Therefore, BM was not combined with peroxydes and i t was reduced as much as possible (0.1. to 0.3%). F i n a l properties are summarised i n Tables 2 and 3. Table 2 presents a comparison between two series of blends with different compositions. The system containing 25% p o l y o l e f i n shows very poor mechanical properties, especially t e n s i l e strength at break


3.

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Coreoctive Polymer Alloys

LAMBLAETAL.

( a ) , which i s largely increased by the introduction of block copoB lymer (KRATON G 1650). The t e n s i l e strength i s also increased in the presence of lower amounts of p o l y o l e f i n by adding reactive BM to the mixture which does not contain the amphiphilic copolymer (KG). Inversely, the e f f e c t due to the presence of KG only leads to a higher performance i n t e n s i l e strength and impact behaviour. Further addition of BM has the e f f e c t of reducing these c h a r a c t e r i s t i c s somewhat. D

Table 2 : MECHANICAL PROPERTIES OF PS/PE BLENDS


Composition {%)

NOTCHED 2 (kJ/BT)

ELASTIC MODULUS 10.MPa

OB

I S

PS

PE

KG

BM

10.MPa

(%)

-

-

94

75

1.8

2900

7,5

-

350

15

2.0

2950

15

-

-

330

6

2.1

3250

85

15

-

0.5

430

7

1.8

3400

85

15

2

-

470

8

2.7

3400

85

13

2

0.5

450

9

2.4

3400

75

25

75

17,5

85

Table 3 : MECHANICAL PROPERTIES OF PS/PE - APP BLENDS

Composition {%) PS

PE

APP

°B KG

e

B

(%)

BM 10.MPa

-

85

12

85

12

3

85

10

3

2

85

10

3

2

3

-

* ELASTIC IS MODULUS (UNNOTCHED) 10.MPa (kJ/rn )

357

12.0

18

0.2

386

14.4

20

3500

-

430

14.4

30

4400

0.2

430

14.2

42

4700

3500

The r e s u l t s obtained with the l a s t series o f blends containing 3% a t a t i c polypropylene are summarised i n Table 3. I t i s interesting to note a limited, but general, increase i n elongation at break, Eg. Furthermore, the influence of both amphiphilic copolymer and reactive BM lead to s a t i s f a c t o r y overall mechanical properties, especially modulus and impact strength. Even i f i t seems d i f f i c u l t to e s t a b l i s h the r e a l contribution of the reactive species, i t i s clear that interpolymeric bonding between PS and LDPE due to the presence of the added BM i s not s u f f i c i e n t to create i n t e r f a c i a l


74


e f f i c i e n t adhesion. However, the f i n a l compromise (last l i n e i n Table 3) shows a positive influence of BM. INTERPOLYMERIC CONDENSATION REACTIONS a. PMMA-AM/PS BLENDS


Condensation reactions i n the melt between the anhydride groups of a copolymer containing maleic anhydride links and hydroxylated o l i g o styrenes were carried out i n discontinuous or continuous mixers. As shown previously (23), the progress of condensation reactions are e a s i l y followed by the r i s i n g consistency i n the melt, if dihydroxylated oligomers are used (Figure 3). The speed constants of these reactions were determined by rheological studies (24). The influence of reciprocal m i s c i b i l i t y between the methacrylic copolymer containing c y c l i c anhydride groups and the styrenic oligomers was investigated i n the case of monohydroxylated oligomers, which were also prepared by anionic polymerisation of styrene and further deactivation with ethyleneoxide. The d i f f u s i o n of these reactive smaller species i s d i r e c t l y influenced by their molecular weight (M ). Table 4 shows the r e s u l t s obtained with three d i f f e r e n t oYigomers of increasing M and a copolymer synthesised on a laboratory scale, containing 10 wt$ c y c l i c anhydride. Table 4 : INTERPOLYMERIC CONDENSATION IN THE MELT PMMA/AM - PS (OH)

PS (OH) GRAFTING YIELD (%) Mn (kg/mol)

2.45

6.85

9.0

wt %

46

55

25

100

12.5

100

75.5

46

40

49

24.5

56

73.5

0

Mw = 72 kg/mol : MA ; 10 wt % B.W.


3.


LAMBLAETAL.

75

Table 5 : INTERPOLYMERIC CONDENSATION IN THE MELT PMMA/AM* - PS (OH)

PS (OH) Mn (kg/mol)


3.8

wt %

GRAFTING YIELD SOLVENT EXTRACTION

(%) GPC

50

34

30

37 5

52

39

25

67

47

12 5

74

49

* HW 55 (ROHM) Mw = 130 ; MA

: 20 wt %

The grafting y i e l d , f i r s t evaluated by a solvent extraction technic, decreases as expected with increasing molecular weight, and i t i s also influenced by mixture composition. It appears that, with this f i r s t copolymer backbone of a rather low molecular weight (Mw = _72 kg/mole , there i s no r e a c t i v i t y l e f t with products where Mw equals 9kg/mol . Table 5 confirms these results with an i n d u s t r i a l copolymer (HW 55, supplied by ROHM), of a higher molecular weight (Mw = 130). In this case, the l i m i t i n g molecular weight of the poorly compatible oligomer i s approximately 4 kg/mol. However, i t was confirmed by GPC analysis that i t i s possible to attain high levels of grafting by mixing during approximately 10 minutes i n the RHEOCORD discontinuous device. The grafted chains were stable at high temperatures and the reversible reaction mentioned by several authors (25-29) was not observed. This point was confirmed recently by studying the reverse reaction with hemiester copolymers of various alcohol chain lengths. The reverse reaction i s d i r e c t l y governed by the s t e r i c hindrance introduced by alcohol chain length and/or nature (30). This grafting reaction was extrapolated to continuous-extruding systems but i t was necessary to increase residence-time and mixing e f f i c i e n c y i n order to obtain the optimal l e v e l of g r a f t i n g (24). This study confirmed that interpolymeric condensation reactions are e f f e c t i v e i n the melt, but f i n a l reactivity is a function of composition and reciprocal m i s c i b i l i t y of the two polymeric species. Further studies on crosslinking reactions in compatible reactive systems (31) have confirmed that d i f f u s i o n plays an important role but surprisingly, the introduction of a t e r t i a r y amine, acting as catalyst, produces a m u l t i p l i c a t i o n of the rate constant by a factor of 100.


76


b. PP/PA 6 BLENDS: Radical grafting of maleic anhydride on PP


As indicated above, i t i s d i f f i c u l t to attach polar reactive groups onto a polypropylene backbone. The grafting was first carried out i n solution and extrapolated to melt mixing (32, 33). It i s necessary to define the compromise between grafting y i e l d and chain degradation i n r a d i c a l grafting of maleic anhydride We carried out experiments to define the optimal conditions in a reactive extrusion process, and to obtain maleic anhydride grafted polymers of polypropylene copolymers (3050 MN 4 supplied by ATOCHEM). The previous studies were carried out i n a batch mixer (HAAKE RHE0C0RD), at a temperature of 220° C and a mixing speed of 64 rpm, during 20 minutes. Three different systems were tested : i . with pure maleic anhydride ; i i . i n the presence of a solvent (toluene or chorobenzene) ; i i i . by introduction of a stoechiometric amount of maleic anhydride and styrene. Dicumyl peroxyde was used as i n i t i a t o r . It i s important to note that a l l the ingredients were introduced simultaneously in the mixing c e l l . The p r i n c i p a l results are summarised i n Figure 4. The three curves represent the variation of grafted versus added maleic anhydride for three different systems, containing the same amount of dicumyl peroxyde (0.48 wt % ) . Curve a, representing pure maleic anhydride grafting, confirms the limited value of r a d i c a l grafting : 0.3%. In the presence of stoechiometric amounts of butylacrylate or styrene, a l i n e a r variation of grafted versus added c y c l i c anhydride i s observed. I t i s important to note that the best grafting yields are obtained with styrene, leading to modified PP containing a few per cent of grafted l i n k s . The melt-index characterisation of these products shows a decrease of MFI versus grafted c y c l i c anhydride (Fig. 5). In the presence of styrene as a comonomer, the grafting reaction seems to be predominant and therefore, the chain degradation by 3 - s c i s s i o n i s reduced. This was confirmed by GPC analysis. Cross-propagation of styrene and maleic anhydride, both i n solvent or i n bulk, i s well known. This behaviour i s attributed to a charge-transfer complex (CTC) between maleic anhydride and styrene and can lead, i n solution, to spontaneous copolymerisation (34,35). Even i f CTC has been confirmed by spectroscopy, i t i s characterised in a few cases only, one of them being based on a stoechiometric mixture of N-vinylpyrrolidone and maleic anhydride (36). However, as mentioned by SEYMOUR et a l . (37, 38), the s t a b i l i t y of a CTC decreases as polymerisation temperatures increase, furthermore, for the styrene-MA pair the charge-transfer complex should be non-existent above 130° C. However, alternating styrene-co-MA and other MA copolymers have been grafted on a variety of other polymeric materials (39,40,41). Our own results further confirm the contribution of CTC to general activation of the grafting reaction. It i s important to note that the grafting e f f i c i e n c y


Coreoctive Polymer Alloys

LAMBLA ET AL.

CH. »CH —C I C0 CHj

-CH—CH^

2

i

2

I

2

CH, CH I I HO —(CH )—C — ( C H ) — C 2

2

3

CH, CH, I I C—(CH )—C—(CH )~OH 3

2

2


© 66 6 o=c I Q

c=o

-C I 0=C

C=0

I OH

I OH %

F i g u r e 3: I n t e r p o l y m e r i c c o n d e n s a t i o n PS and copolymer PMMA/AM .

—-OH

between d i h y d r o x y l a t e d

MA •

ST

MA (X B . N . ) Q

F i g u r e 4: G r a f t i n g o f m a l e i c a n h y d r i d e on PP: g r a f t i n g y i e l d v e r s u s monomer c o n c e n t r a t i o n .


78


observed when the reaction i s carried out i n a discontinuous mixer i s also v e r i f i e d i n a continuous process, using a twin-screw from WERNER PLEIDERER (ZSK 30). However, i n this case i t i s essential to adjust feeding conditions of the various reagents, as shown i n Figure 4 by the two points (black c i r c l e and black square), where grafting y i e l d varies from 0.65% to 0.95% for two d i f f e r e n t ways of feeding. Further characterisation of the grafted PP before and after solvent p u r i f i c a t i o n have confirmed the alternating copolymerisation between styrene and MA.


c. PP/PA BLENDS: Interpolymeric r e a c t i v i t y Polyamide-6 (PA-6) and polypropylene (PP) are both semi-crystalline polymers and the combination of an engineering p l a s t i c (PA) and the best commodity product (PP) could lead to new blends with interesting intermediate properties. We tested systems containing 50 wt% of each product and the ones obtained by addition of 3% of the reactive PP-g-AM r e s u l t i n g from previous continuous g r a f t i n g i n the extruder. The blends were prepared by simple mixing i n the ZSK 30 twin-screw extruder and the samples for mechanical testing were molded by i n j e c t i o n i n a BILLION equipment. Table 6 summarises the most important data r e s u l t i n g from s t r e s s s t r a i n analysis. These four blends were obtained successively by simple melt-mixing (YM0), blends containing maleic anhydride grafted products i n presence of a solvent: chlorobenzene (YM 1) and two products obtained by alternating grafting with styrene (YSM 2 - YSM 3). Due to the lower molecular weight of the grafted polypropylene, i t seems easier to obtain a rapid and e f f i c i e n t mixing with YM 1 which results i n a higher value of e l a s t i c modulus. The two blends containing PP-g AM/ST exhibit higher values both i n elongation and y i e l d - s t r e s s , which could be connected with better i n t e r f a c i a l adhesion.

Table 6 : MECHANICAL PROPERTIES OF BLENDS

REFERENCE

E

(MPa)

e

(%)

ay

(MPa)

YSM 0

1900

6

35

YSM 1

2900

25

40

YSM 2

2180

29

43.8

YSM 3

2180

29

42



3.

LAMBLAETAL.


79

The two Figures 6 and 7, scanning electron micrographs of fracture surfaces, show a great difference i n p a r t i c l e size and i n t e r f a c i a l adhesion between the 50/50 blend and the l a s t one, YSM 3, containing 3% of the reactive PP-g AM/ST. The unreactive blend shows a large p a r t i c l e size (Figure 6), i r r e g u l a r shapes and poor i n t e r f a c i a l adhesion. The reactive one (Figure 7) i s c h a r a c t e r i s t i c of a dispersion of small spherical p a r t i c l e s i n a continuous matrix and apparently, s a t i s f a c t o r y i n t e r f a c i a l adhesion. However, these r e s u l t s do not represent the optimised system. It appears that d i r e c t reactive blending between two homopolymers and the corresponding reactive product could lead to f a i r mechanical properties. The amphiphilic grafted copolymer, r e s u l t i n g from condensation reaction between c y c l i c anhydrides grafted onto PP and primary amino chain ends of PA (Figure 8) i s produced during the melt mixing, leading to the expected decrease of i n t e r f a c i a l tension and to higher cohesion of the blend.



80


F i g u r e 6: Scanning e l e c t r o n micrographs o f f r a c t u r e PP/PA w i t h o u t c o m p a t i b i l i z e r .

F i g u r e 7: Scanning e l e c t r o n micrographs o f f r a c t u r e PP/PA w i t h 3 wt % PP-g AM .

surface:

surface:


3. LAMBLAET AL.



RUBBER

MODIFIED

PA

imidif ication

Figure 8; Reaction scheme of interpolymeric condensation between MA 6 and PP-g AM. CONCLUSIONS Industrial examples and further laboratory studies confirm that the performance of blended immiscible polymers not only depend on their mechanical nature and blend composition, but may be further improved by chemical reactions conducted during melt-mixing. The compatibiliser needed f o r p a r t i c l e size reduction and further i n t e r f a c i a l adhesion may be formed by interpolymeric grafting through co-reactive micromolecular species or grafting and end-capping condensation reactions. Studies based on reactive systems containing copolymers of methyl methacrylate and maleic anhydride confirmed the e f f i c i e n c y of melt-mixing condensation reactions, taking into account the reciprocal p a r t i a l m i s c i b i l i t y of the polymeric species. The engineering blend obtained by mixing PP and PA-6, i n the presence of a small amount of a reactive grafted polypropylene, seems to be of the greatest interest f o r intermediate materials with a satisfactory price-performance r a t i o . LIST OF SYMBOLS PMMA : Polymethylmethacrylate PS : Polystyrene PS (OH) : Hydroxylated polystyrene PE : Polyethylene LDPE : Low density PE PP : Polypropylene KG : Kraton G (block copolymer) PA 6 : Polyamide 6 PP- g AM : Polypropylene grafted with maleic anhydride PP-g AM/ST : PP grafted with maleic anhydride and styrene


81

82


M M wt IS

: Molecular weight (number average) : Molecular weight (weight average) % : Percent by weight : Impact strength : Tensile strength at break £ : Elongation at break MA : Maleic anhydride ST : Styrene BuA : Butylaerylate MA : Grafted maleic anhydride g n

n


REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.

Wu, S. Polymer 1985, 26, 1855; J. Appl. Polym. Sci. 1988, 35, 549. Wu, S. Polym. Eng. Sci. 1987, 27, 335. Teyssie, P.; Fayt, R.; Jerome, R. Makromol. Chem., Macromol. Symp. 1988, 16, 57. Leibler, L. Makromol. Chem., Macromol. Symp. 1988, 16, 1. Natansohn, A.; Murali, R.; Eisenberg, A. Makromol. Chem., Macromol. Symp. 1988, 16, 175. Teyssie, P.; Fayt, J.; Jerome, R. Proc. ACS Meeting, Toronto 1988, 58, 622. Cimmino, S.; D'Orazio, L.; Greco, R.; Maglio, G.; Malinconico, M.; Mancarella, C.; Martuscelli, E.; Palumbo, R.; Ragosta, G. Polym. Eng. Sci. 1984, 24, 48. Flexman, E.A. Polym. Eng. Sci. 1979, 19, 564. Wu, S. J. Polym. Sci., Polym. Phys. 1983, Ed. 21, 699. Chen, D.; Kennedy, J.P. Polym. Bull. 1987, 17, 71. Borggreve, R.J.M.; Gaymans, R.J.; Luttmer, A.R. Makromol. Chem. Macromol. Symp. 1988, 16, 195. Sneller, J.A. Mod. Plast. Int. 1985, 42. Gotoh, S.; Fujii, M.; Kitagawa, S. SPE ANTEC 1986, Techn. Pap., 32, 54. Devaux, J.; Goddard, P.; Mercier, J.P. Polym. Eng. Sci. 1982, 22, 229. Hobbs, S.Y.; Dekkers, M.E.J.; Watkins, V.H. Pol. Bull. 1987, 17, 341. Hobbs, S.Y.; Dekkers, M.E.J.; Watkins, V.H. "Polyblends-88" NRC/IMRI Symp., Boucherville Que-Canada, April 5-6, 1988. Coran, A.Y. Polym. Proc. Eng. 1988, 5, 317. Juliano, P.C. US-France Workshop 1988, Williamsburgh. Teyssie, P.; Fayt, R.; Jerome, R. Makromol. Chem., Macromol. Symp. 1988, 16, 41. Fayt, R.; Jerome, R.; Teyssie, P. J. Polym. Sci., Polym. Phys. 1981, Ed. 19, 1269. Fayt, R.; Jerome, R.; Teyssie, P. J. Polym. Sci. in press. Heikens, D.; Hoen, N.; Barentsen, W.; Piet, B.. Ladan, H. J. Polym. Sci., Polym. Symp. 1978, 62, 309. Lambla, M.; Killis, A.; Magnin, H. Europ. Polym. J. 1979, 15, 489. Lambla, M.; Druz, J. Preprints IUPAC, Amherst 1982, 2, 487. Muskat, I.E. U.S. Patent 3 085 986.



3. LAMBLA ET AL.


83

26. Whithworth, C.J.; Zutty, N.L. U.S. Patent 3 299 184. 27. Zimmerman, R.L. U.S. Patent 3 678 016. 28. Ardashnikov, A.Y.; Kardash, I.Y.; Praveonikov, A.N. Polym. Sci. USSR 1971, 13, 2092. 29. Barozier, G.; Niclo, A. French Patent 2 130 561. 30. Lambla, M.; Mazeres, F.; Druz, J. Preprints AICHE Meeting, New York 1987, 40B. 31. Lambla, M.; Satyarayana, N.; Druz, J. Makromol. Chem. 1988, 189, 0000. 32. De Vito, G. J. Polym. Sci. 1984, 22, 1335. 33. Ide, F. Kobunshi Kagaku 1968, 25, Nr 274. 34. Tsuchida, E.; Tomono, T. Makromol. Chem. 1972, 151, 245. 35. Vukovic, R.; Kurusevic, V.; Fles, D. J. Polym. Sci. 1977, 15, 2981. 36. Nikolaev, A.F.; Bondarenko, V.M.; Shakalova, N.K. Syn. High Polym. 1974, 1974, 81. 37. Seymour, R.B.; Garner, D.P.; Stohl, G.A.; Sanders, L.J. Am. Chem. Soc., Div. Polym. Chem. Prepr. 1976,17,(2)660. 38. Seymour, R.B.; Garner, D.P. J. Coat. Technol. 1976, 48 (612), 41. 39. Gaylord, N.G. Adv. Chem. Ser. 1973, 129, 209. 40. Gangarz, I.; Laskavski, W. J. Polym. Sci. Polym. Chem. 1979, Ed. 17, 3, 683. 41. Gangarz, I.; Laskavski, W. J. Polym. Sci. Polym. Chem. 1979, Ed. 17, 5, 1523. RECEIVED April 27, 1989


Coreactive Polymer Alloys - American Chemical Society

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